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I am using windows 7. my c: drive capacity is 75 gb. where the Os is located. The size of the files on the disk is only 50 gb including hidden files. But used space of c drive shows 60Gb. Where the 10gb space goes? I think it might be due to the files that are burned to a dvd disk long time before. every time burn a files to a dvd. size of C: drive gets increased. how to resolve the problem? how to get back my disk space?

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migrated from serverfault.com Apr 20 '13 at 11:03

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Fragmentation!! –  Daniel R Hicks Apr 20 '13 at 12:01
    
An additional part of it may be system restore images, which happen for most driver installs/updates and somewhat randomly as windows awkwardly does. Download the free ccleaner, navigate to Tools > System restore. You should have quite a few options to remove. If you want to limit the hard drive space those take, I can post that too. –  nerdwaller Apr 20 '13 at 12:51
    
Fragmentation has NOTHING to do with this!!!! See my answer below –  cybernard Apr 20 '13 at 19:27
    
@cybernard - Uh, what you describe is known as "internal fragmentation". –  Daniel R Hicks Apr 20 '13 at 20:17

3 Answers 3

The size calculated by adding up file sizes in Windows Explorer is known to be inaccurate. The only correct usage figure is in the 'pie' chart. There are a number of Microsoft articles which explain some of the places the space can be.

http://blogs.technet.com/b/askcore/archive/2013/03/01/where-did-my-space-go.aspx

http://blogs.msdn.com/b/ntdebugging/archive/2008/07/03/ntfs-misreports-free-space.aspx

http://blogs.msdn.com/b/ntdebugging/archive/2008/10/31/ntfs-misreporting-free-space-part-2.aspx

You can also use programs like Treesize and WinDirStat to investigate.

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All drives are formatted, and as such lose a portion of their total capacity. For example a 2TB Hard Drive only has 1.81GB Usable space after it is formatted.

This is because the partition table takes up the part of the drive you cannot see.

http://en.wikipedia.org/wiki/Disk_partitioning

^ Hope this helps a bit more.

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A 2TB disk shows as 1.81TB in Windows because of the different ways disk manufacturers and Microsoft measure storage. Disk manufacturers use the normal decimal method where 1TB = 1,000,000,000,000. Microsoft uses a binary based system where 1K = 1024 so that 1TB = 1,099,511,627,776. –  David Marshall Apr 20 '13 at 12:01

First listen to the other people who have already stated the different between a gigabyte and a billion bytes. A 75gb hard drive really stores about 69.8gb of stuff.

Second, when you store a file it uses a minimum of 1 cluster, and has to use whole number of clusters. You can not allocated 2.5 cluster, it is really 3 clusters.

Here is a functional example. Lets say your cluster is 4k (or 4096 bytes) if you save a document on your hard drive that is 1,000 bytes then 3096 bytes of space are wasted. The end of every single file on the hard drive generates some amount of waste. The only except are files that are exactly sized in increments of 4k. So 4096 multiplied by any whole number.

If you have collection of 1,000 icons using 1000 bytes on a 4k cluster then each one wastes 3096 bytes. Roughly 3k. 3k *1000 = approx 3 megabytes of wasted space.

Every file system has this basic issue. You can adjust the cluster size on some file systems with in certain limits. FAT is the least flexible. FAT32 is slightly flexible. NTFS has the most flexibility of all the windows file systems. It is possible with NTFS to have a cluster size of 512 bytes, and this reduces the waste to less than 1% but some waste still exists.

To clear up the fragmentation non-sense. Fragmentation, just makes it harder for the operating system to find the entire file slowing down access to the file. It can not increase or decrease the amount of available space.

However, it is possible that the software you are using creates the DVD in a temporary file and then burns the file. After the file is burnt it likely deletes the file and you get some hard drive space back. DVD can be as large as 4.6gb or 8.5gb if it is dual layer. A deletion of a temporary file of this size would make a big impact on free space on a hard drive of this size.

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If this does not completely account for the space you could have a more than 1 partition on your hard drive and one of them could be hidden. Check "Disk Management". –  cybernard Apr 20 '13 at 19:50
    
What you're describing is known as "internal fragmentation". –  Daniel R Hicks Apr 20 '13 at 20:21
    
@DanielRHicks While the wikipedia page does say that, it does not make it true. Even wikipedia says "this article has multiple issues". Dictionary.com "fragmentation" definition #4. The space at the end of the cluster is simply slack or wasted space. Fragmentation is breaking a file into parts to fill available free spaces that are to small for the whole file. The wasted space has to be less than 1 cluster(even by a single byte) and therefore the wasted space can not be fragmented. –  cybernard Apr 21 '13 at 16:56
    
I first heard that definition in 1972 or 1973. Explained by David A. Nelson, a respected consultant. You can argue that the terminology is poorly chosen, but you cannot (validly) argue that the term does not mean what I said it means. –  Daniel R Hicks Apr 21 '13 at 20:38

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